Containment pens for finfish aquaculture

ABSTRACT

A containment pen for finfish aquaculture, comprising a supporting structure, a net attached to the supporting structure and defining a containment volume for containing finfish, wherein the net comprises a plurality of removable net panels, wherein each of the removable net panels comprises a discrete piece of flexible netting attached along its perimeter to one or more substantially rigid members, and wherein the removable net panels are configured to be removable from the containment pen with the piece of flexible netting remaining attached to the substantially rigid members.

Cross-Reference To Related Application

This application is a continuation application of and claims priority toU.S. application Ser. No. 12/416,062, filed on Mar. 31, 2009, which is acontinuation of and U.S. application Ser. No. 11/851,625, filed on Sep.7, 2007, which is a continuation application of U.S. application Ser.No. 10/976,641, filed on Oct. 29, 2004.

TECHNICAL FIELD

This invention relates to containment pens for marine finfishaquaculture.

BACKGROUND

Marine finfish aquaculture uses pens to contain the finfish and toprevent access by predators. A typical pen consists of a net suspendedat the surface by a floating structure (e.g., a circular plasticcollar). The walls of the net extend vertically from the water's surfaceto a depth of typically 6 to 20 meters, and then across the bottom ofthe pen.

Over the past 30 years, the size of containment pens has increased.Early containment pens were 40 meters in circumference (or 15 metersquare). Today's standard containment pen is 100 meters incircumference, with a volume of 6,000 to 20,000 cubic meters. A singleaquaculture farm operation can have 30 of these circular pens.

The nets used in these pens are huge. Dry, they weigh several tons andat the end of a growing cycle they can weigh 20 tons or more owing tofouling from marine organisms such as algae and mussels. The handling ofthese huge nets for repair and maintenance has become a huge logisticaland economic problem for fish farmers. Too bulky and heavy to handle,nets must be cut off the pens, often ending up on the ocean bottomwhere, according to newly issued discharge permits, they must berecovered.

Suspended nets are subject to deformation from currents, sagging, andbagging. This can result in pockets where predators such as seals canpush in to bite fish, with resulting tears to the net. Therefore, thesepens need a predator net, a secondary, coarser net entirelyencapsulating the containment net. The predator net is typicallysuspended from the outside of the floating circular collar, and thecontainment net from the inside of the collar, to keep a one meterseparation between predator and containment nets. This is generallybelieved to be sufficient to keep predators from pushing into thecontainment net.

A third net has to be incorporated into the current technology—a birdnet is suspended above the surface pens to prevent access to the pens bypredator birds, e.g., osprey, eagles, herons, and gulls.

Suspended net systems are generally located nearshore, where seaconditions (e.g., waves and winds) are less severe, and access iseasier. But offshore locations are known to have advantages. Waterdepths are greater, thus permitting the containment pens to be submergedduring storm conditions when fish would naturally move to greater depthsto avoid damage from wave action. Water quality is generally better, asthere is less pollution from land sources. The containment pens have amuch reduced aesthetic presence, and thus face less politicalopposition. Greater water circulation through the pens helps dilutewaste products. Water temperatures are more stable. Risk of disease isreduced due to increased distance between farms.

Notwithstanding the known advantages of offshore locations, the art hasnot yet found a practical design for offshore containment pens, althoughvarious ideas have been advanced.

Willinsky U.S. Pat. No. 5,251,571 shows an offshore containment pen inthe shape of a geodesic sphere formed of hubs and interconnectingstruts. Two hemispheric nets are attached to the interior of the sphere,by attaching the net at many points (col. 4, lines 3-18). The sphere canbe lowered below the ocean surface, and it can rotated at the surfaceusing an axle and buoyant elements incorporated into the sphere.

Zemach U.S. Pat. No. 5,412,903 proposes a metal skeleton with asuperimposed netting covering the skeleton.

Bones U.S. Pat. No. 5,628,279 shows fish cages designed to be raised andlowered along the submerged support columns of offshore oil platforms.The pens rely on injection-molded, fiberglass-reinforced grating panelspainted with antifouling paint. The grating panels are supported in arigid, generally hexagonal structure. An optional net may be installedif the fish are too small to be contained by the grating panels.Loverich U.S. Pat. No. 7, 617,813 (Ocean Spar Technologies) discloses asubmersible pen having a central vertical spar and a peripheral ring,with a net stretched around the peripheral ring to the two ends of thespar. Similar structures are in use in various locations, and pens aslarge as 3,000 cubic meters have been constructed. E.g., the SubmersibleSea Station from Net Systems.

Sadco, a Russian company, has proposed a submerged metal cage from whicha net is hung.

Another approach to offshore pens has been to strengthen the design ofsurface pens. E.g., the Dunlop Tempest pen uses flexible rubberizedflotation collars filled with gas at high pressure supporting gravitynets. The pens have been used in Ireland for salmon, and have survivedsubstantial storms. The Ocean Spar pen by Net Systems uses tensionedvertical steel spars supporting gravity nets. Farmocean proposes agalvanized steel superstructure supporting gravity nets.

Another issue in the design of containment pens is moving fish betweenpens or harvesting fish from pens. Conventional approaches are extremelylabor intensive, and stressful for the animals. Workers use a seine netto crowd the fish to one side of a pen and then use a fish pump or brailnet to move the fish. Often many sets of the seine are needed to capturethe fish, and this operation cannot be done in rough weather. The fishare stressed from crowding, and often physically injured (scale loss,bruising, loss of protective slime) from the nets and the fish pump. Theinjuries lead to eventual mortality or downgrading at harvest.

SUMMARY

In a first aspect, the invention features a containment pen for finfishaquaculture, comprising a supporting structure, a net attached to thesupporting structure and defining a containment volume for containingfinfish, wherein the net comprises a plurality of removable net panels,wherein each of the removable net panels comprises a discrete piece offlexible netting attached along its perimeter to one or moresubstantially rigid members, and wherein the removable net panels areconfigured to be removable from the containment pen with the piece offlexible netting remaining attached to the substantially rigid members.

Preferred implementations of this aspect of the invention mayincorporate one or more of the following: The net panels may provide thesupporting structure for a majority of the containment pen. The netpanels may be in the shape of a polygon. The substantially rigid membersmay comprise structural beams, and the net panels may comprise at leastthree beams joined at their ends to define the polygonal shape.Adjoining net panels may be attached by fastening together adjoiningbeams. The panels may be shaped so that a beam of one panel extendsgenerally parallel to and adjacent a beam of an adjoining panel, and thetwo adjacent beams may be attached by fasteners. The fasteners may beremovable to permit a panel to be removed from the pen. The pen may besubstantially spherical. The pen may be a geodesic structure. The panelsmay comprise one or more triangular panels making up the geodesicstructure. The discrete pieces of flexible netting may be tensionedgenerally in a plane defined by the one or more substantially rigidmembers. The containment pen may further comprise flotation memberssupported on at least some of the beams. The flotation members maycomprise fixed flotation members sized to provide substantially neutralbuoyancy to the containment pen. The flotation members may compriseinflatable flotation members sized and positioned to permit the pen tobe rotated to a selected position by selective inflation of theinflatable members.

In a second aspect, the invention features a containment pen for finfishaquaculture, comprising a supporting structure, a net attached to thesupporting structure and defining a containment volume for containingfinfish, wherein the supporting structure comprises a plurality ofremovable panels, and wherein the removable panels make up a majority ofthe supporting structure.

Preferred implementations of this aspect of the invention mayincorporate one or more of the following: The removable panels whenattached to adjoining removable panels may provide the structuralintegrity of the majority of the supporting structure. The removablepanels may be in the shape of a polygon. The removable panels maycomprise at least three beams joined at their ends to define thepolygonal shape. Adjoining net panels may be attached by fasteningtogether adjoining beams. The panels may be shaped so that a beam of onepanel extends generally parallel to and adjacent a beam of an adjoiningpanel, and the two adjacent beams may be attached by fasteners. Thefasteners may be removable to permit a panel to be removed from the pen.The pen may be substantially spherical. The pen may be a geodesicstructure. The panels may comprise one or more triangular panels makingup the geodesic structure. The containment pen may further compriseflotation members supported on at least some of the beams. The flotationmembers may comprise fixed flotation members sized to providesubstantially neutral buoyancy to the containment pen. The flotationmembers may comprise inflatable flotation members sized and positionedto permit the pen to be rotated to a selected position by selectiveinflation of the inflatable members.

In a third aspect, the invention features a containment pen for finfishaquaculture, comprising a supporting structure, a net attached to thesupporting structure and defining a containment volume for containingfinfish, wherein the net comprises a plurality of net pieces separatefrom other net pieces, wherein each of the plurality of net pieces isattached along its perimeter to one or more substantially rigid members,and wherein the net pieces are tensioned generally in a plane defined bythe one or more substantially rigid members.

Preferred implementations of this aspect of the invention mayincorporate one or more of the following: The substantially rigidmembers may define the perimeters of polygons across which the netpieces are tensioned. The polygons may be joined to form a pen that issubstantially a geodesic structure with net stretched tightly acrossgeodesic panels. The net pieces may be attached along the length of thesubstantially rigid members by trapping the perimeters of the net pieceswithin keyways running along the rigid members.

In a fourth aspect, the invention features containment pens and fishtransfer apparatus for finfish aquaculture, comprising at least a firstand a second containment pen, each of the first and second containmentpens comprising a supporting structure, a net attached to the supportingstructure and defining a containment volume for containing finfish, andan underwater aperture in the net that can be selectively opened orclosed; a fish transfer conduit configured to be connected to theunderwater aperture of the first and the second pen, to provide anunderwater fish transfer conduit for transferring fish under their ownlocomotion between the first and second pens; and a structure forreducing the volume of the first containment pen available to the fishto encourage fish to transfer from the first pen to the second pen byswimming through the fish transfer conduit.

Preferred implementations of this aspect of the invention mayincorporate one or more of the following: The structure for reducing thevolume of the first containment pen available to the fish comprises maybe an expandable member that progressively fills the interior of thefirst pen. The expandable member may comprise a balloon element that maybe filled with water or gas or a combination of gas and water. Theaperture may be positioned in a panel that replaces a removable netpanel of the containment pen.

In a fifth aspect, the invention features a method of transferring fishbetween containment pens in finfish aquaculture, the method comprisingconnecting a fish transfer conduit to an underwater aperture in thefirst and in the second containment pen, to provide an underwater fishtransfer conduit for transferring fish under their own locomotionbetween the first and second pens; and reducing the volume of wateravailable in the first pen to encourage fish to transfer from the firstpen to the second pen by swimming through the fish transfer conduit.

Preferred implementations of this aspect of the invention mayincorporate one or more of the following: Reducing the volume of wateravailable in the first pen may comprise progressively raising the firstpen partially above the surface of the water. The first pen may beraised above the surface of the water by progressively increasing theamount of gas contained in flotation chambers within portions of thefirst pen. Reducing the volume of water available in the first pen maycomprise expanding the volume within the first pen occupied by anexpandable member. The expandable member may be a balloon element thatis filled with gas or water or a combination of gas and water.

In a sixth aspect, the invention features a containment pen for finfishaquaculture, comprising a generally spherical supporting structure, anet attached to the supporting structure and defining a generallyspherical containment volume for containing finfish, and inflatableelements positioned at a plurality of locations around the supportingstructure, wherein the inflatable elements are sized and positioned sothat inflation of selected ones of the inflatable elements has theeffect of rotating the pen to a selected orientation.

Preferred implementations of this aspect of the invention mayincorporate one or more of the following: The containment pen mayfurther comprise pneumatic lines for delivering inflation air to theselected ones of the inflatable elements. The supporting structure maycomprise a plurality of interconnected beams, and the inflatableelements may be contained substantially within the interiors of thebeams.

Among the many advantages of the invention (some of which may beachieved only in some of its various aspects and implementations) arethat the containment net is divided into pieces of manageable size, thuspermitting individual pieces to be inspected, removed, replaced, orrepaired on a regular maintenance schedule. The containment net can bestretched tightly enough to make a predator net unnecessary, and toallow the pen to be towed when stocked with fish. A separate bird net isalso not necessary, as the net panels serve as bird netting when abovethe surface of the water. Fewer parts are required to construct the pen,as many of the panels and net pieces are identical. The resulting penhas great strength for its weight, particularly in the case of thepanels forming a geodesic sphere. The pens can be manufactured atrelatively low cost, as the parts can be prefabricated in a factory, andassembled on the site of the aquaculture facility. Assembly anddisassembly at sea is possible. Different size pens can be manufacturedfrom the same basic parts. The pen can be rotated to bring differentpanels to the surface for access, inspection, maintenance, repair, orreplacement. A panel or group of panels can be removed without loss offish, as a panel or group of panels needing to be removed can be broughtabove the water surface. Fish can be transferred between pens undertheir own locomotion, with less stress on the fish. Containment pensretain their shape and volume regardless of the forces imposed bycurrents. Other features and advantages of the invention will be foundin the detailed description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one possible implementation of theinvention.

FIG. 2 is a perspective view of the implementation of FIG. 1 with onepanel enlarged for clarity.

FIG. 3 is a perspective, cross-sectional view through the structure of apanel.

FIG. 4 is a perspective, cross-sectional view showing the attachment ofone panel to adjoining panels.

FIGS. 5A-5C are cross-sectional views through different possible panelbeams.

FIGS. 5D-5E are perspective views of possible panel beams.

FIG. 5F is a perspective view showing the manner of installing nettingto a panel beam.

FIG. 5G is an elevation view showing the fastening holes and handholdsalong a panel beam.

FIG. 5H is an elevation view showing one possible manner of fasteningtwo adjoining panel beams.

FIGS. 6-6A are perspective views of a containment pen submerged and atthe surface.

FIG. 7 is a perspective view of four containment pens secured to amooring grid.

FIG. 8A is a perspective view of a fish transfer apparatus that can beused with the containment pens.

FIGS. 8B-8I are diagrammatic views illustrating a fish transferoperation using the transfer apparatus of FIG. 8A.

FIG. 9 is a perspective view of a containment pen configured forcollection and removal of organic detritus from the bottom of the pen.

FIG. 10 is a perspective view of the junction between five panels, andthe installation of a rounded member at the junction to protect the fishin the vicinity of the junction.

DETAILED DESCRIPTION

There are a great many possible implementations of the invention, toomany to describe herein. Some possible implementations that arepresently preferred are described below. It cannot be emphasized toostrongly, however, that these are descriptions of implementations of theinvention, and not descriptions of the invention, which is not limitedto the detailed implementations described in this section but isdescribed in broader terms in the claims.

FIG. 1 shows a finfish containment pen 1 having a plurality ofindividual net panels 2, which when fastened together form a generallyspheroid geodesic structure about 30 meters in diameter. The pen mayvary in shape and size, and need not be a geodesic structure. FIG. 2shows an enlargement of one net panel 2, which is formed by joiningthree side beams 3 and netting 4. In the 30 meter pen shown in FIGS.1-2, there are 80 separate and distinct net panels. Larger pens could beassembled using the same panels, e.g., pens having 180, 320, or up to720 panels.

The structure of a net panel is shown in more detail in FIG. 3. Eachside beam 3 may be formed from an extruded member shaped to the properangles according to the desired geometry of the pen. The side beam 3could be made from extruded plastic or aluminum, or it could befabricated, for example by welding or otherwise adhering individualpieces of material (e.g., by welding steel). Beams may be joined attheir junctions by welding (e.g., HDPE or metal can be readily welded)or using another fastening technique. Fixed foam flotation 6 could beadded internally to beam 3, in sufficient amounts to give the panelneutral buoyancy. An inflatable flotation tube 5, made of a fabricmaterial such as Hypalon™ could also be added internally to beam 3.

FIG. 4 shows two adjoining net panels attached to the net panel of FIG.3. Beam 3 a of a first adjoining net panel is fastened to one of beams 3b of the center net panel. Beam 3 c of a second adjoining net panel isfastened to the other of beams 3 b. Bolts 7 or another type of fastenerare used to attach the adjoining beams 3 a, 3 b 3 c. A piece of netting4, which may vary in mesh size according to the size of the fishcontained in the pen 1, is secured to beams 3 b by a strip of metal orplastic 9 which is fastened in slot 10 in each beam. Many othertechniques can be used for securing the perimeter of the netting. FIG. 4shows only a portion of two beams of a panel. Typically, all beams of apanel (e.g., all three for a triangular panel) would be attached toadjoining panels, and to the piece of netting 4, in the same mannershown.

FIG. 4 shows an alternative extrusion detail for beams 3 b and 3 c, inwhich a flange 8 is provided that both strengthens the beam and, due tothe clamping action of the bolt 7 below the flange, advantageouslyforces the interior joint of beams 3 b and 3 c closed. The additionalflange 8 could also be used to attain a dihedral angle from a stock 90degree angle extrusion.

FIG. 5A shows a cross section through one of beams 3. The fixed foamflotation member 6, the inflatable flotation tube 5, and a pneumaticpressure line 11 for supplying flotation gas (e.g., air) to theinflatable flotation tube 5 are installed internally within the extrudedbeam 3. None of these three members is necessary, and each may beprovided without the other. The extruded beam is segmented along itslength (not shown), so that flotation member 6, flotation tube 5, andline 11 are surrounded by water when the pen is submerged.

If a pneumatic line 11 is provided, it may be connected through valves(not shown) to the inflatable flotation tubes 5, and pneumaticconnections may be made between net panels with quick connect aircouplings (not shown). Even if flotation tubes 5 and pneumatic lines 11are used, it is not necessary that they be used in all panels. Some ofthe net panels 2 may have side beams with only fixed flotation 6 asshown in FIG. 5B. And some panels may have neither fixed nor inflatableflotation members.

Another implementation of a side beam 3 of the net panel 2 is shown inFIG. 5C. In this case, the side beam has no separate flotation member,and relies for flotation only on that inherent in the material used forconstruction. Depending on the material used for the beams, it may notnecessary or desirable to provide separate flotation members, orflotation could be provided by members external to the panels (notshown), or by special flotation panels that replace net panels (notshown).

FIG. 5C also shows an alternative technique for fastening the pieces ofnetting 4 to the side beam 3 of the net panel 2. In this case, thenetting 4 is sewn with a bolt rope 14 around the perimeter of the net 4,and the bolt rope 14 is threaded through a key-shaped slot 13 which runsthe entire length of the tangential section of beam 3.

FIG. 5D is a perspective view showing a side beam 3 in which a keyshaped slot 13 is molded into the edge of beam 3. Holes 31 in the beam 3are configured to receive a through fastener to connect two adjacent netpanels (e.g., as shown in more detail in FIG. 5H). A handhold 32 isprovided for allowing a person to securely grasp the beam 3 when workingon the containment pen.

FIG. 5E shows two beams 3 of the type shown in FIG. 5D, with the beamspositioned as they would be after being fastened together (but withoutfasteners shown).

FIG. 5G is an elevation view of beam 3 of FIG. 5D, showing connectorholes 31 and handholds 32 spaced along the beam 3 in such a way as tomate with adjacent net panels.

FIG. 5F is a perspective view showing one of many possible netattachment techniques. The netting 4 is stretched over the net panelside beam 3, and a flexible plastic or rubber strip 33 is forced intothe key slot 13 in order to retain the net. An advantage of thistechnique is that when panels 2 are fastened together (as shown in FIG.5E), the net retaining strips 33 cannot be removed.

One technique for fastening net panels together is shown in FIG. 5H. Ametal U-shaped retainer 41 is slipped over the exterior flanges of matedbeams 3 so that a hole 44 in the retainer 41 matches a hole 31 in eachof the beams. A metal pin 42 (e.g., stainless steel) is inserted throughthe holes 44 and 31. A spring clip 43 is rotated to lock the pin 42 intoplace.

The containment pen 1 preferably neutrally buoyant, with buoyancyprovided both by the materials used in construction (e.g., use of HighDensity Polyethylene (HDPE) for beams 3) and/or by fixed foam flotationmembers 6. The inflatable flotation tubes 5 may be individually inflatedby activating valves supplying air through pneumatic lines 11, so thatwhen a particular flotation tube or group of tubes is inflated, the penrotates to bring the selected net panel or group of net panels to thesurface of the water (or to the top of the pen if the entire pen issubmerged). Depending on which flotation tubes 5 are inflated, the netpen 1 can be oriented so that generally any net panel 2 can beselectively moved to the surface of the water (or to the topmostposition if the pen is fully submerged). Other techniques can also beused to rotate the pen.

An advantage of being able to rotate any given net panel 2 to thesurface of the water (or a top orientation) is that the operator of thecontainment pen can then inspect, remove, replace, clean, and maintainall of the net panels from the surface without having to dive below thesurface of the water. Also, bringing different sections of the pen abovewater periodically will reduce the amount of fouling of the nets frommarine organisms.

The containment pen can be operated either fully submerged below thesurface of the water or partially submerged. If the pen is outfittedwith inflatable flotation tubes 5, they can be used to help raise andlower the pen from a submerged to a partially submerged position. FIG. 6shows one option for mooring a single net pen 1. Mooring lines 15 can beattached to any number of net panel 2 junctions or hubs 16 to distributethe load forces over a wide area. In the implementation shown in FIG. 1,in which there are 80 net panels, there are 32 hubs 16, any of which canbe used for mooring. If the net pen were to be rotated, the mooringlines would be relocated to the hubs 16 appropriate to whichever netpanel 2 was brought to the topmost position. FIG. 6 also shows thebundled umbilical cord 17 through which feed, compressed air, andelectrical cabling (e.g., for cameras or sensors) flows to the net pen1. The umbilical cord goes from the net pen 1 to a surface buoy 18. Thesurface buoy 18 or similar device provides the electrical cables,compressed air, and feed for the net pen 1. FIG. 6A shows the samesingle point mooring with the net pen at the surface, only partiallysubmerged. The single point mooring technique could also be used if asingle net pen were being towed by another vessel.

It is anticipated that in many situations multiple net pens will beinstalled in nearby locations. In this case, the single point mooringshown in FIG. 6 would typically be replaced with a mooring arrangementsuch as shown in FIG. 7, wherein a fixed submerged grid 21 is held intension by the anchors 60, mooring blocks 61, anchor lines 20. The pensare attached to the grid by mooring lines 22. The net pens are normallyattached to the grid 21 by four mooring lines 22. When conditionspermit, two opposing mooring lines 22 can be dropped, and the net penrotated on an axis formed by the remaining two mooring lines 22. Thepens an be rotated in many orientations by selecting which pair ofmooring lines to leave attached. In this way, an operator may generallybring any net panel to the surface.

The containment pens could also be operated as free drifting systemswithout moorings, or as semi-drifting systems attached to a motorizedvessel.

Finfish aquaculture requires periodic handling of fish for transferbetween pens, grading for size distribution, inventory, and harvesting.These activities as currently practiced are usually stressful on theanimals, causing injury and loss of growth. The containment pens shownin the figures, owing to their modular external structure, lendthemselves to the transfer of fish between net pens or into a harvestingpump with minimal stress. FIG. 8A shows a single panel 23 that has beenmodified to form a transfer link between two net pens or between asingle net pen and a harvest pump. Instead of there being netting 4installed in panel 23, a substantially rigid material is installed, tosupport a collar 24 that extends outward from the panel. Internal to thecollar 24 is a gating device 25, e.g., an iris diaphragm, which controlsthe passage of fish. In FIG. 8 a the iris diaphragm 25 is closed. Thegating device 25 can be pneumatically controlled by the operator at thesurface. One end of a transfer tube 26 is attached to the collar 24, andthe other end of the transfer tube 26 is attached to a similar collar ona second pen, or to a fish harvest pump. A transfer sequence, in whichfish are moved under their own locomotion from one pen to another, isillustrated diagrammatically in FIGS. 8A-8F. In FIG. 8B, one or morepanels 27 at the top of one pen have been modified to accept a packagedinflatable displacement balloon 28, which can be filled with air orwater by the operator at the surface. In FIG. 8B. the deflated balloon28 has been lowered into the net pen suspended from the tube 30, whichcontains lines for air and water. The pen 1 containing the balloon hasbeen attached to a second pen 1 a via a transfer tube 26 as described inthe above paragraph. When it is time to transfer fish, the operatoropens the gate 25 in both net pens, as shown in FIG. 8C. The balloon 28is slowly inflated with air 50, water 51, or a combination of air andwater. Filling the top portion of the displacement balloon 28 with airwill lift the balloon 28 as it fills. Balloon 28 may be fitted withcircumferential flexible weighted rings 29, which ballast the balloon asit fills. As the balloon 28 slowly inflates the available swimmingvolume in net pen 1 decreases. Fish naturally migrate to less crowdedspaces, and will swim through the transfer tube 26 into net pen 1 a asshown in FIG. 8D. A grading panel in the transfer tube (not shown) wouldallow smaller fish to pass through to net pen 1 a while retaining largerfish in net pen 1. Likewise, the transfer tube could contain fishcounting and biomass estimation devices.

At the end of the transfer process, or when the appropriate number offish have been transferred or harvested, the operator may close the gate25 in both net pens as suggested in FIG. 8E. The transfer tube 26 canthen be removed, and the balloon 28 deflated and retracted into panelgroup 27. Panel group 27 can then be removed for service andrepackaging.

An alternate transfer sequence is shown in FIGS. 8F-8I wherein pen 1 ais attached to pen 1 with a transfer link as above. The operator opensthe gates 25 in both pens, then raises pen 1 to the surface by addingbuoyancy. As pen 1 rises out of the water, fish swim through thetransfer link into pen 1 a.

The modular nature of the containment pen described allows forindividual net panels to take on many functions, and to be removed andreplaced as the functions change. Individual panels or groups of panelsmay be modified for access, feeding, harvest, mooring, flotation, andcollection of detritus from the bottom of the net pen. For example, FIG.9 shows a collection device for collecting dead fish and feces from thebottom of the pen. A group of panels 29 has been modified at the bottomto funnel organic waste into a collection tube 38. At location 39compressed air is forced into tube 30 such that an uplift is caused,forcing a vacuum effect bringing to the surface the organic detrituswhich has collected at the bottom of the net pen.

In the implementations shown in the figures, the hub junctions at whichthe net panels meet are tight fitting, and may be subject to wear fromfriction. FIG. 10 shows a possible spool-shaped member 70 which can beinstalled through a hole 71 at a hub junction. Flange 72 is toothed withappropriate sized teeth to grip the interior of the containment pen,allowing flange 73 to be unscrewed and removed. This allows removal orreplacement of any of the net panels 2. The exposed spool end 72 isrounded and smooth to protect the fish within the net pen 1.

Many other implementations of the invention other than those describedabove are within the invention, which is defined by the followingclaims. For example, a few of the possibilities are outlined as follows.

In the disclosed implementation, the removable panels serve asstructural panels to provide the supporting structure of the pen, and asnet panels to provide the netting for fish containment. In someimplementations, the removable panels could serve only one or the otherof those functions. For example, the net panels might be non-structural,and attached to an underlying structural frame, which, for example,could be a geodesic structure formed in the conventional manner ofstruts joined at hubs. Alternatively, the removable panels might providethe structure of the containment pen, but not the containment netting,which could be a conventional net hung from the structure.

It is not necessary that the entire surface of the pen be covered byremovable net panels, or that the structure of the pen be providedentirely by removable structural panels. E.g., one or more portions ofthe pen could use a conventional structure in which the structuralelements and/or the netting is not divided into removable panels, andonly the remaining portions of the pen employ the removable panelfeatures.

The pen could have many shapes and many structural forms; e.g., it neednot be a geodesic structure, nor be spherical in shape.

The netting need not be attached to the panels in the manner shown inthe figures. Many other attachment techniques are possible. And a singlepiece of netting might extend across more than one panel.

The netting tension aspects of the invention, in which pieces of nettingare attached along their perimeters to one or more substantially rigidmembers, and tensioned generally across a plane defined by thosemembers, can be practiced without use of the removable panel aspects orother aspects of the invention.

The fish transfer aspects of the invention, in which fish are encouragedby a reduction in available swimming volume to transfer from one pen toanother under their own locomotion, can be practiced without use of theremovable panel aspects or other aspects of the invention.

The selective flotation aspects of the invention, in which a sphericalpen is rotated to an orientation with a selected portion of the penbrought to the surface, can be practiced without the use of theremovable panel aspects or other aspects of the invention.

1-11. (canceled)
 12. A method of cultivating aquatic life forms in anaquaculture containment pen, the aquaculture containment pen including aplurality of panels configured to form a substantially sphericalcontainment volume suitable for cultivating aquatic life forms, eachpanel of the plurality of panels including at least three substantiallyrigid beams and a discrete piece of netting attached along its perimeterto the at least three substantially rigid beams, the method comprising:disposing the aquaculture containment pen in an offshore locationsuitable for cultivating aquatic life forms; disposing a plurality offish in the containment volume; submerging the aquaculture containmentpen; raising the aquaculture containment pen to the surface after aperiod of time; accessing the containment volume; and harvesting atleast a portion of the plurality of fish.
 13. The method of claim 12,wherein the aquaculture containment pen is assembled at the offshorelocation suitable for cultivating aquatic life forms.
 14. The method ofclaim 12, wherein the containment volume is accessed by removing atleast one panel of the plurality of panels from the aquaculturecontainment pen.
 15. The method of claim 12, wherein the aquaculturecontainment pen further includes one or more flotation members, the oneor more flotation members configured to be filled with gas to raised thecontainment pen to the surface.
 16. The method of claim 12, whereinraising the aquaculture containment pen to the surface after a period oftime allows at least one of cleaning, repairing, removing, and replacingone or more of the plurality of panels.
 17. The method of claim 12,wherein the method further includes rotating the aquaculture containmentpen to bring at least a portion of the plurality of panels to thesurface to allow at least one of cleaning, repairing, removing, andreplacing of one or more of the plurality of panels.
 18. The method ofclaim 17, wherein the aquaculture containment pen further includes aplurality of flotation members, the plurality of flotation membersdisposed on the aquaculture containment pen such that inflating one ormore of the plurality of flotation members rotates the aquaculturecontainment pen to bring at least a portion of the plurality of panelsto the surface.
 19. The method of claim 17, wherein the aquaculturecontainment pen is secured by four mooring lines such that each mooringline is coupled to the aquaculture containment pen at a polar locationand each mooring line is disposed substantially opposite to anothermooring line, and wherein the aquaculture containment pen is rotated byuncoupling any two opposing mooring lines and rotating the aquaculturecontainment pen about the axis formed by the remaining two mooringlines.
 20. The method of claim 12, wherein the period of time is a firstperiod of time, the method further comprising: submerging theaquaculture containment pen for a second period of time; and raising theaquaculture containment pen to the surface after the second period oftime.
 21. A method of transferring at least a portion of fish from afirst aquaculture containment pen to a second aquaculture containmentpen, each of the first containment pen and the second containment penincluding a plurality of panels configured to form a substantiallyspherical containment volume suitable for cultivating aquatic lifeforms, each panel of the plurality of panels including at least threesubstantially rigid beams and a discrete piece of netting attached alongits perimeter to the at least three substantially rigid beams each ofthe first aquaculture containment pen and the second aquaculturecontainment pen submerged below a surface of water, the methodcomprising: coupling a first end of a conduit to a first panel of thefirst aquaculture containment pen, and coupling a second end of theconduit to second panel of the second aquaculture containment pen;opening an occlusion device included in at least one of the first panel,the second panel, and the conduit; urging at least a portion of the fishto travel from the containment volume of the first aquaculturecontainment pen to the containment volume of the second aquaculturecontainment pen under their own locomotion via the conduit; and closingthe occlusion device.
 22. The method of claim 21, wherein the methodfurther includes raising the first containment pen above the surface ofthe water to urge at least a portion of the fish to travel from thecontainment volume of the first aquaculture containment pen to thecontainment volume of the second aquaculture containment pen under theirown locomotion via the conduit.
 23. The method of claim 22, wherein themethod further includes accessing the containment volume of the firstaquaculture containment pen to remove dead fish and feces.
 24. Themethod of claim 21, wherein the method further includes reducing thecontainment volume of the first aquaculture containment pen, thereduction in containment volume urging at least a portion of the fish totravel from the containment volume of the first aquaculture containmentpen to the containment volume of the second aquaculture containment pen.25. The method of claim 24, wherein the first aquaculture containmentpen includes an expandable member disposed in the containment volume ofthe first containment pen, wherein the expandable member is deflated ina first configuration, the expandable member configured to be inflatedwith air or water in a second configuration such that the inflatedexpandable member substantially fills the containment volume of thefirst aquaculture containment pen thereby reducing the containmentvolume of the first aquaculture containment pen.
 26. A method ofassembling an aquaculture containment pen, the aquaculture containmentpen including a plurality of panels configured to form a substantiallyspherical containment volume suitable for cultivating aquatic lifeforms, each panel of the plurality of panels including at least threesubstantially rigid beams and a discrete piece of netting attached alongits perimeter to the at least three substantially rigid beams, themethod comprising: slipping a U-shaped retainer over an exterior flangeof mating beams of each of the adjacent panels of the plurality ofpanels such that a hole in the retainer is adjacent to and substantiallymatches a hole in each of the mating beams; inserting a pin through thehole in the retainer and the hole in each of the beams; and rotating aspring clip to lock the pin in place.
 27. The method of claim 26,wherein the method further includes disposing a spool-shaped member atone or more hub junctions formed at corners of the beams of the adjacentpanels, the spool-shaped member passing through a hole at a hub junctionand removably coupled to a flange.
 28. The method of claim 26, whereinthe U-shaped retainer is formed from a metal.
 29. The method of claim26, wherein the U-shaped retainer is formed from a plastic.
 30. Themethod of claim 26, wherein the assembled aquaculture containment pen isa geodesic sphere.
 31. A method of removing organic detritus collectedat the bottom of a finfish aquaculture containment pin, the aquaculturecontainment pen including a plurality of panels configured to form asubstantially spherical containment volume suitable for cultivatingaquatic life forms, each panel of the plurality of panels including atleast three substantially rigid beams and a discrete piece of nettingattached along its perimeter to the at least three substantially rigidbeams, the method comprising: coupling a collection tube to at least oneof the plurality of panels which is located at a bottom of theaquaculture containment pen relative to a surface of water in which atleast a portion of the aquaculture containment pen is submerged;creating a vacuum in the collection tube; and removing the organicdetritus from the bottom of the aquaculture containment via thecollection tube.